Hilbert curve fractal antenna for dual on- and off-body communication

We present a Hilbert curve fractal antenna operating at 2.45 GHz ISM and 5.5 GHz WLAN bands. The proposed antenna employs a third-order Hilbert curve and two shorting vias for antenna miniaturization and dual-band/mode operation. At 2.45 GHz, the antenna exhibits a monopole-like radiation pattern, while at 5.5 GHz, it provides a broadside radiation pattern, suitable for simultaneous on- and off-body communication using two distinct frequency bands. The antenna footprint is as small as 25.5 mm × 25.5 mm. Simulation and measurement results demonstrate that the antenna gain is more than 1.9 dBi if the antenna is mounted on a ground larger than 40mm × 40 mm. The effect of human body presence on antenna performance was investigated by means of full-wave simulations locating the antenna on a human body phantom. It is shown that the proposed antenna is capable of maintaining its free-space performance over the human body phantom except for the gain reduction of 2.5 dBi at 5.5 GHz band.